Page 84 - Jabalpur_EQ

Chapter 4 Mud&Village Houses

Absence of Roof Truss
Most inclined roofs of rural houses had no roof truss. A typical arrangement of
wooden members supporting the roof is shown in Fig. 4-7. An attic for storag
was often prepared by supporting beams on walls and beams were not connected
to the roof. Twigs or bamboo sticks were laid running perpendicular to these
beams which supported them. Similar sticks were placed on the roof beams in a
perpendicular direction on which fired clay tiles (khaprail) were laid. During the
earthquake the beams on these lean-to roofs tended to push the walls outward in
the absence of adequate ties. This caused damage to the upper regions of the
walls and a separation between the inclined portions of the roof. Such a separa-
tion was observed even when no other damage was caused. Figure 4-8 shows a
typical damage caused due to inadequate roofing system. Moreover, dislodging
of the roofing material (clay tiles) was a commonplace as they were not appropri
ately tied together and to the bamboo grid (Fig. 4-9).

Inadequate Connections
In the absence of adequate connections and ties, during the earthquake the roofs
could not restrain the out-of-plane movements of the walls. It is very important
for the structural integrity or robustness of the structure that all structural com-
ponents shouid be tied together. Figure 4-10 shows damage to walls in the
absence of a proper roof and wall connection.

Roof beam
wood members

wooden beam
constituting an attic

wall

Figure 4-7. The roof arrangement.

Jabalpur Earthquake of May 22, 1997 74